Burglar-alarm



B. F. KRAFT BURGLAR ALARM.

(No Model.)

No. 476,945. Patented June 14, 1892.

UNITED STATES PATENT OFFICE.

BENJAMIN F. KRAFT, OF READING, PENNSYLVANIA.

BURGLAR-ALARM.

SPECIFICATION forming part of Letters Patent No. 476,945, dated June 1 4, 1892.

Application filed January 21,1892 $erial No. 418,796. (No model.)

To (all whom, it may concern.-

Be it known that I, BENJAMIN F. KRAFT, a citizen of the United States, residing at Head ing, in the county of Berks, State of Pennsylvania, have invented certain Improvements in Burglar-Alarms, of which the following is a specification.

My invention relates to that class of alarms which are adapted to be operated by the turning of a door-knob or an equivalent manner, and the principal purpose of which is to serve as a burglar-alarm, though adapted, also, to be usednnerely as a call-bell. Heretofore a variety of devices have been provided for this purpose; but so far as I am aware they have been more or less unsatisfactory either on account of complicated construction, imperfect operation, or inconvenience in removing and attaching.

My object has been to provide an improved device which will overcome all these objections, and it is fully described hereinafter in connection with the accompanying drawings.

Figure 1 is a front elevation of my device with the casin g removed to show the interior mechanism. Fig. 2is a side elevation with the casing shown in section. Fig. 3 is a front elevation with the casing in place. Fig. at shows the knob-gripping device, and Fig. 5 a modified meansof operating the trigger mechanism.

The operating mechanism is allinclosed in a two-part sheet-metal casing A A, upon which is mounted on a post I) the alarm-bell B. The alarm-movement is of a well-known form, consisting, mainly, of the winding-arbor E, having a clock-spring e, a main wheel c, and a ratchet (not shown) attached thereto, a toothed wheel F, and pinion f, the latter meshing with the main wheel 6, and a verge o meshing with the toothed wheel, pivoted to an arbor c, and earryin g the alarm-hammer O by means of its stem 0. In order to produce my improved device, I have combined with this simple and well-known alarm-movement certain mechanism which I will now proceed to describe.

A trigger mechanism controls the alarmhammer. This consists of a slide bar H, mounted on the front and rear plates D and D of the alarmmovement and provided with an arm 71 which when the bar is pushed inward by meansof a stem 7L2, projecting through an opening a in the front of the casing A, engages the stem 0 of the alarm-hammer, as shown in Fig. 1, so as to prevent oscillation of the latter, but which is normallypressed forward by a spring 7L, thus releasing the ham- A stop it on the end of this slide-bar is engaged by the upper end of a lever G when the trigger is set and the hammer thus hold,

This lever is pivoted at g to the plate D and weighted at its lower end g, so that it normally assumes a vertical position. In addition to this trigger mechanism a positive look ing device K is provided, consisting of a hellcrank pivoted at 7.; to the plate D and arranged to engage or release an arm 0 on the verge arbor or sleeve by which the hammer is carried. This boll-crank is operated by means of a lever k which projects through the front casingA.

The means for attaching the device to doorknobs preferably consists of a clamp M, of spring-wire, which is forked to span the knobshank and hugs the knob L, so as to cause the whole alarm device to turn with it.

hen the spring is wound up, the alarmhammer is ordinarily prevented from oscil lating by the positive locking device K. In order to use the device on a door, it is hung upon the knob by means of the spring-clamp, as heretofore described. To set the alarm, the sliding bar H is pushed in by means of its projecting stem 7L2, and the upper end of the weighted lever Gr is swung in front of the stop 7L. The locking device K is then moved out of engagement, and the hammer is held only by the arm 7L2 of the slide-bar and is ready to act upon any movement of the outside knob. The effect of such move ment is to turn the whole alarm device with the knob. The weighted lever, however, tending always to remain plumb, releases the slide-bar H, which is moved outward by its spring it, thus leaving the hammer free to swing against the bell, which it continues to do until the mainspring eis run down or the locking device K is again thrown into engagement with it.

An opening or glass (1 may be provided in the casing to facilitate setting the trigger mechanism; but this may be readily dispensed with. The lever G may be swung to one side by means of a projection g which extends through a slot a in the casing.

Though my device is more especially adapted to be applied to door-knobs, it may obviously be used elsewhere. It may, for instance, be applied to the meeting-rail of a Windowsash, so as to be operated by an attempt to lift the same. In this case a device such as is shown in Fig. 5 maybe employed to turn the lever G and release the hammer. This consists of a wire N, shaped at one end to engage the shank g of the lever G and at the other end 91 to engage the Window-frame, being preferably bent at n to form a spring and passing through a slot in the side of the casing A.

Having thus described my invention, I do not limit myself to the exact construction shown; but

What I claim is- 1. In an alarm device, the combination; with thealarm-movement having a verge carrying the alarm-hammer, of a trigger mechanism comprising a spring-retracted slide-bar having an arm arranged to engage the alarm' hammer and a pivoted lever adapted to engage a stop upon said slide-bar, and means for operating the lever to release the ham mer, substantially as set forth.

2. In an alarm device, the combination, with the alarm-movement having a verge carrying the alarm-hammer and provided with an arm, of a trigger mechanism, means for operating the same to release the hammer,

and a locking mechanism for said hammer,

bar, a pivoted bell-crank having one of itsv ends adapted to engage said arm of the verge and its opposite end provided With operating means extending through a Wall of the easin g, and means for releasing the bell-hammer. In testimony whereof I affix my signature in presence of two Witnesses.

BENJAMIN F. KRAFT. Witnesses:

HARRY E. MILLER, HENRY MILLER. 

